Method of making field rings



' Sept. 17 11929 F. A. HAUGHTQN METHOD OF MAKING FIELD RINGS Filed Oct.26, 1926 2 Sheets-Sheet. l

Sept. 17, 1929. F. A. HAUGHTQN 1,728,895

METHOD OF MAKING FIELD RENGS Filed Oct. 26, 1926 V 2 Sheets-Shea}; 2

Inventor i Patented Sept. 17, 1929 UNITED STATES PATENT OFFICE FRANK.A.EAUGHTON, OF SGHENEOT ADY, NEW YORK, ASSIGNOB TO Gm ELEG- TRIC COMPANY,A CORPORATION OF NEW YORK METHOD OI MAKING- I'IELD BRIG-S Applicationfiled October 26, 1926. Serial No. 144,886.

My invention relates to the -manufacture of ring-shaped structures andparticularly to field rings for direct current dynamo-electric machines.A common practice in the past has been to construct such field rings ofgray iron or steel castings, the latter being preferred by reason oftheir more suitable magnetic properties and greater strength.

'20 uniformity in magnetic properties inasmuch as hidden defects arelikely to exist which are not easily detected. For these and otherreasons the use of rolled steel for the field frames of largedynamo-electric machines has been recognized as highly desirable butbecause of the high cost of frames so made there has been little, ifany, inducement to make such a substitution. This high cost is duefirst, to the cost of the material employed, for example plate stock oreven forgings, and

second to the ,cost of labor or special machines or both for shaping thematerial to the proper form. These considerations are particularlyimportant in the case of machines of large size.

It is an object of my invention to provide improved steel rings suitablefor the field frames of dynamo-electric machines which are superior toand which may be manufactured at lower costs than the rings now usedtogether with the process of their manufacture. As a result of myinvention large economies are obtained both by reason of the materialemployed and the simple and inexpen- 5 sive method utilized in workingthat material, the use of s ecial and expensive tools and highly skillelabor being rendered unnecessary.

.In accordance with my invention I construct rings of a comparativelycheap form of rolled steel, namely, rerolling slabs or forging billetsthese being the terms generall applied in the trade to the product ofthe st rolling process to which the steel is sub ected in the steel millafter the casting of the ingot. The surface of these slabs, which termwill be used hereafter for convenience to apply to both rerolling slabsand 1jiggingbillets, have a more or less rough and 1s ed surface buthave" magnetic properties which are superior to those of steel castlugsto the extent that they can be made ma terially smaller in cross sectionfor the same capacity machine. K In utilizing these slabs in accordancewith my invention I pass them while at a forging temperature one or moretimes as may be found necessary throu h common bending rolls to givethem the esired curvature. As a result of this rolling process a slabwill be bent uniformly throughout its length with the exception of thetwo end portions, which as is well known to those skilled in the art,will remain more or less straight. The slab having been given thedesired curvature is removed from the bending rolls and the straight orimproperly bent end portions are then out off by means well known to thesteel worker. The end faces of the bent sections are then machined toobtain a flat surface and suitable means are provided for securing endto end the ring segments thus formed. Suitable supporting brackets orfeet also may be secured to one. or more of the ring segments.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed outin the appended claims.

Referring to the drawing, Fig. I shows-a rerolling slab as it appearswhen received from the rolling mill; Fig. 2 shows the same slab beingbent in the bending rolls; Fig. 3 shows the bent slab after removal fromthe bending rolls; and Fig. 4 shows a dynamoelectric machine having asplit field magnet constructed in accordance with my invention of twosuch bent slabs, the armature and the bearing supports therefor beingomitted.

The rerolhng slab 1, shown by ltself in Fig.

1, as has already been pointed out above is the product of the firstrolling process to which the ingot is subjected in the steel mill. It ismore or less crooked and unshapely and dis tinctly shows the imprint 2of the ragging rolls between which it is passed in this first rollingprocess. The slabs also usually have one or more blisters or otherdefects on their surfaces which it is the practice of the mill to cutaway by hand before further rolling of the slabs. lln the present use'of the slabs, however, such defects are not objectionable and need notbe removed. Slabs are obtained in various sizes 1n accordance with thesizesof the machines to be constructed, for ex-.

ample, the slab shown in Fig. 1 is about eight and one half inches thickand about twentythree feet long, weighing approximately seven tons.

The slab is first uniformly heated in a suitable furnace to a forgintemperature whence it is removed and while ot is passed through commonbending rolls. In Fig. 2 I have shown the slab 1 being passed'throughthe bending rolls 3 which are variously conthe slab through the bendingrolls also hasthe effect of partially smoothing out the ragging andother irregularities on the surface of theislab as shown in Figs. 2, 3and 4 and what remains is an advantage rather than an objection since itprovides a better surface to which may cling the putty and paint finishof the machine. The slab is thus given the desired bend throughout thegreater portion of its length but its two end portions 6 will remainsubstantially straight or unbent for a certain distance, as indicated onthe drawing. These end portions 6 will be referred to hereafter asunbent inasmuch as they do not have the curvature of the intermediateportion of the ring. If the field ring being constructed 1s to comprisetwo ring segments of 180 degrees each, as illustrated by way of examplein the drawing, the length of each slab must be suflicient to obtain the180 degrees of the intermediate or uniformly bent portion plus theunbent end portions. After the bending operation is complete the slab isremoved from the bending rolls and the unbent ends {5 are cut 0Esquarely, the line of out 01f being indicated by the dotted lines 7 inFig. 3. In cutting off the ends suflicient material maybe left to allowfor subsequent machining if necessary to obtain flat end faces. The endmasses portions which have been cut off while constituting a waste is inreality only small amount in comparison with the remaining segment andhas relatively small value being more than offset by the saving in laborand material resulting from this method. In a I have shown the two ringsegments secured together by bolts 9 passing through lugs 10 at theadjacent ends of the ring segments, also the lower ring segment providedwith supporting brackets or feet 11. The lugs and feet may be secured tothe ring segments in any suitable manner for example by welding and Ihave found it to be of some advantage to secure the lugs 10 to the ringsegments so that the lugs and the end faces of the ring segments may bemachined simultaneously whereby a larger area of contact is providedbetween the adjacent surfaces of the segments. After securing thesegments together the ring 12 formed thereby may be machined on itsinner surface to which field pole pieces, shown for example at 13 havingwindings 14, may be attached. The end faces of the field ring may alsobe machinedto which end heads may be secured for supporting thearmature, brush holders, etc.

As has been pointed out above the field frames of dynamo-electricmachines heretofore have commonly been made of steel castings. As iswell known, castings require'patterns which in the case of largemachines are in themselves costly. Variations in shrinkage and draftrequirements of castings necessitate due allowance in the dimensions ofthe parts and in the making ofsteel castings moreover it is necessaryalso to provide large swells and projections for risers. In thefinishing process all this excess material must be machined oifrequiring much time and labor. 7

By using rerolling slabs a pattern is not reuired, he ring segments canbe formed much 0 oser to size and more nearly circular, no draftallowance need be provided and there are no swells or riser projectionsto be machined off. Hence there is a decided economy in weight and incost of machining off surplus metal. As rings formed of rerolling slabsdo not contain blow holes, sand holes, scabs, etc. there is no loss dueto such defects which are inherent with castings. Moreover such ringsare not subject to commutator troubles in the completed machine whichsometimes occur where cast frames are used in which hidden defects arepresent. The magnetic proper ties of rerolling slabs of low carboncontent of say .1 to 2% carbon are very satisfactory as compared withiron or steel castings and experience has shown that frames made fromsuch slabs may be constructed materially lighter in net'weight. In thedesign of machines with cast steel frames 2. flux'fdensity of 75,000lines per square inch heretofore has been allowed but with frameconstructedof lao masses 3 rerolling slabs a flux density of 90,000lines is being regularly employed, due to their greater permeability.

Rerolling slabs having been given only the 5 first rolling and hencesubject to a minimum labor costare the cheapest form of so-calledsemi-finished steel and can be purchased at the present time for aboutone quarter of the price of steel castings. This saving in initial costof material taken together with the economies resulting from the abovedescribed method of formin a finished ring from that material has been%ound in the case of a number of machines to amount to from 30% to 40%in factory costs of the finished frames ready for the attachment ofpoles and other parts.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. The method of forming a ring-shaped member from steel slabs whichcomprises passing the slabs through bending rolls to give them thedesired curvature, cuttin ofi the unbent end portions, and joining theent portions end to end.

2. The method of forming a ring segment from a steel slab whichcomprises passing the slab through bending rolls to bend only a portionintermediate the ends thereof to the desired curvature and then cuttingofi the unbent end portions. 7

3. The method of forming a field ring for a dynamo-electric machine fromthick steel slabs which comprises passing the slabs in a heatedcondition through bending rolls to form ring segments, cutting ofi theunbent end portions of each segment to form flat end faces and securingthe segments together end to end.

4. The method of forming a split field ring for a dynamo-electricmachine from rerolling slabs which comprises heating the slabs, passingthem through bending rolls to form ring segments and to produce a moresmooth surface, cutting off the unbent end portions of the segments,machining the end faces and firmly securing the segments together toform a ring.

In witness whereof, I have hereunto set my hand this 23rd day ofOctober, 1926.

FRANK A. HAUGHTON.

